A significant amount of research and development has been undertaken in recent years towards environmental clean-up operations, and in particular to the purification and decontamination of ground water, waste water, and drinking water. A variety of techniques have been used in the prior art to destroy or remove contaminating and toxic materials such as trace organic and inorganic compounds; substances which produce color, taste and odor; pathogenic bacteria; and harmful suspended materials.
These techniques include the use of shock waves created by ultrasonic vibrations and exposing the water to ultraviolet radiation (see, for example, U.S. Pat. No. 6,071,473 to Darwin; U.S. Pat. No. 5,230,792 to Sauska and EP 959046 to Yoshinaga et al.).
Electricity has also been employed as a decontamination agent, such as by introducing positively charged ions into a water stream to cause coagulation and separation of particles, and by the passing of electric current within a fluid chamber (see, for example, U.S. Pat. No. 4,917,782 to Davies; U.S. Pat. No. 5,531,865 to Cole; U.S. Pat. No. 6,346,197 to Stephenson; and U.S. Pat. No. 6,331,321 to Robbins). In this case, the current flowing between the anode and cathode has a toxic effect on microorganisms nearby.
The utilization of ozone for the purification and disinfection of water is a known and effective technique (see, for example, U.S. Pat. No. 4,352,740 to Grader et al.; U.S. Pat. No. 4,382,044 to Baumgartner; U.S. Pat. No. 4,767,528 to Sasaki et al.; U.S. Pat. No. 5,266,216 to Agueda; U.S. Pat. No. 5,683,576 to Olsen; U.S. Pat. No. 5,711,887 to Gastman et al.; U.S. Pat. No. 6,068,778 to Steiner at al; U.S. Pat. No. 6,146,524 to Story U.S. Pat. No. 6,419,831 to Wang; and U.S. Pat. No. 6,402,945 to Swales et al.). However, it has not yet come into widespread use, such as the general acceptance and widespread use of chlorine.
Various techniques for water purification containing organic concomitants based on contacting the water with ozone in the presence of various mixed catalysts are described in U.S. Pat. No. 4,029,578 to Turk; U.S. Pat. No. 5,620,610 to Ishii; U.S. Pat. No. 6,149,820 to Pedersen; and U.S. Pat. No. 6,251,264 to Tanaka. In particular, the heterogeneous catalyst utilized in U.S. Pat. No. 4,029,578 comprises water insoluble salts, for example, insoluble carbonate, sulfate, oxide, halide or sulfide of such metals as copper, cadmium, and group VIII metals, etc.
According to U.S. Pat. No. 6,149,820, the water enriched with ozone is passed through a catalyst, consisting of activated carbon as the carrier for metal oxides including iron oxide, cobalt oxide, nickel oxides, manganese oxide. Furthermore, the catalyst can contain one or more of the noble metals, e.g., platinum or palladium.
A technique is known in the art, sometimes under the name electro-hydraulics, which utilize high-energy electrical discharge into a volume of liquid for the purpose of disinfecting water, changing chemical constituents and recovering metals and other substances from liquids or slurries (see, for example, U.S. Pat. No. 3,366,564 to Allen; U.S. Pat. No. 3,402,120 to Allen et al.; and U.S. Pat. No. 4,957,606 to Juvan). According to this technique, an electro-hydraulic shock wave within the liquid, intensive light radiation and thermo-chemical reactions are initiated by arc discharge into a spark gap formed by the electrodes immersed in the liquid. One of the drawbacks of this technique is associated with the fact that in the repeated discharging of a high-energy electrical arc across the gap between electrodes, the electrodes are rather rapidly eroded and burned up. Similarly, switching components are consumed by burnup.
U.S. Pat. No. 5,464,513 to Goriachev and U.S. Pat. No. 5,630,915 to Green et al. describes a water purification technique which concurrently uses a synergistic combination of pulsed mechanical shock waves, ultraviolet radiation, and ionization of the water stream, as disinfecting and purification actions within the water to be treated. The water treatment system of this technique includes a pair of electrodes extending transversely across and through a discharge chamber. Contaminated water is introduced into the chamber through an intake port where it passes either through or proximate to the discharge area. A pulse power unit delivers a rapid sequence of arc inducing electrical pulses across the electrodes, thereby producing a series of electric discharge arcs across the discharge area between the electrodes. The arcs are of sufficient energy whereby a plasma inducing arc is sustained through the water across the electrodes, generating lethal levels of ultraviolet radiation, as well as mechanical shock waves having the capacity of directly killing microorganisms and weakening others. Furthermore, molecules of water proximate to the discharge area are broken down into excited radicals, including hydroxyl ions and free oxygen, which combine with organic chemicals to eliminate them from the water stream.
RU Pat. No. 2136600 to Boyev et al. describes a technique for water purification by means of barrier high energy electric discharges formed as a result of the application of a pulsed electric field applied between the electrodes to an air-water mixture formed from water jets and drops. The pulsed electric filed is characterized by the pulse duration shorter than 0.5 microseconds, the slope of the pulse's front grater than 109 V/s and the amplitude of the field strength being in the range of 20-100 kV/cm. For this purpose, the high voltage pulses are applied with the frequency higher than 50 Hz. The frequency magnitude f is selected from the condition
  f  ≥      50    ⁢          v      h      where v is the speed of the water flux and h is the height of the electrode system. The values of the pulse parameters were chosen such that the conductivity of the system at these pulse conditions is significantly small, i.e., the water is an electrical insulator.
The electrode system includes a set of electrodes implemented in the form of two combs. One of the combs is coupled to the generator of the high voltage pulses, while the electrodes of the other comb are grounded. The electrodes are covered by an electrical insulating barrier in the form of tubes made of quartz glass.
Various configurations of the electrode system that can be utilized in the device for water purification are disclosed in RU Pat. Nos. 2136601; 2136602 and 2152359 to Ryazanov et al.
In particular, RU Pat. No. 2136601 describes a discharge chamber including a high voltage and grounded electrodes implemented in the form of a volume grid wherein the high voltage electrode is arranged between the grounded electrodes. RU Pat. No. 2136602 describes an electrode system wherein the grounded electrode is in the form of a cylinder, while the high voltage electrode is in the form of a cylindrical brush which is housed within the ground electrode. RU Pat. No. 2152359 describes a discharge chamber including a high voltage electrode is implemented in the form of a volume grid, while the grounded electrode is configured as a perforated partition implemented in the form of hollow cylinders.
U.S. Pat. No. 5,464,513 by Goriachev et al describes a water decontamination system which provides for the passage of an electric discharge through a liquid to be decontaminated.
Each of the systems relying on electrical discharges also includes a fixed separation distance between electrodes, and when the electrodes erode, some form of readjustment of the interelectrode gap becomes necessary. Additionally, the use of an optimal electrode spacing for the selection of a particular nano-particle size is not possible with the prior art configurations.